Method and system for dynamic computed tomography scanning at cyclic displacement points

Abstract

A computed tomography method and system for performing dynamic scans of objects undergoing cyclic displacement, for example a human heart. Characteristic curves are generated from images reconstructed from projection data synchronized with the cyclic displacement of the object. Each image reflects one displacement cycle of the object, and consists of projection data collected, in one case, within a phase window centered on a specified phase of cyclic displacement of the object, and in another case, consists of projection data collected between two specified phases of cyclic displacement.

What is claimed is: 
     
       1. A computed tomographic system for dynamic scanning of an object at cyclic displacements while exposing radiation energy to said object, comprising: (a) scanning means for generating projection data representing a measured characteristic of said object by scanning a portion of said object over a selected time period;   (b) detecting means for generating displacement signals responsive to the cyclic displacement of said object during said time period;   (c) memory means coupled to said scanning means and said detecting means for correlating with respect to time and storing said projection data and said displacement signals;   (d) first selecting means coupled to said memory means for selecting specific phases of cyclic displacement in a region scanned within said object;   (e) reconstructing means coupled to said first selecting means and said memory means for generating a plurality of images of said object from said projection data generated between said specific phases of said displacement signals, each of said images being generated from one displacement cycle of said object;   (f) second selecting means coupled to said reconstructing means for selecting a region of interest in said region scanned within said object; and   (g) dynamic curve display means coupled to said reconstructing means to average said measured characteristic within said region of interest for each of said images and to display said measured characteristic as a function of time.   
     
     
       2. The computed tomographic system of claim 1 wherein said first selecting means selects projection data collected at a fixed phase prior to and after the occurrence of a specified displacement signal. 
     
     
       3. The computed tomographic system of claim 1 wherein said first selecting means selects projection data starting at a first specified phase and ending at a second specified phase. 
     
     
       4. A computed tomographic system of claim 1 wherein said measured characteristic is relative x-ray absorption in said region of interest. 
     
     
       5. A computed tomographic method enabling dynamic scanning of an object at cyclic displacements while exposing radiation energy to said object, comprising: (a) generating projection data representing a measured characteristic of said object by scanning a portion of said object over a selected time period;   (b) generating displacement signals responsive to the cyclic displacement of said object during said time period;   (c) correlating with respect to time and storing said projection data and said displacement signals;   (d) selecting specific phases of cyclic displacement in a region scanned of said object;   (e) generating a plurality of images of said object from said projection data generated between said specific phases of said displacement signals, each of said images being generated from one displacement cycle of said object;   (f) selecting a region of interest within said region scanned of said object; and   (g) averaging said measured characteristic within said region of interest for each of said images and displaying said measured characteristic as a function of time.   
     
     
       6. The computed tomographic method of claim 5 wherein the step of selecting specific phases of cyclic displacement includes selecting projection data collected at a fixed phase prior to and after the occurrence of a specified displacement signal. 
     
     
       7. The computed tomographic method of claim 5 wherein said step of selecting a region of interest includes selecting projection data starting at a first specified phase and ending at a second specified phase. 
     
     
       8. A computed tomographic method of claim 5 wherein said measured characteristic is relative x-ray absorption in said region of interest.